Effect of rye A and B chromosomes on meiotic association of Hordeum marinum ssp. gussoneanum (4x) chromosomes in intergeneric hybrids.
Chromosome association at metaphase I was studied in PMCs of eight H. marinum ssp. gussoneanum (4x) x rye hybrids. Differences in the levels of association separated six hybrids with 2n = 23 including 14 Hordeum, 7 rye A and 2 rye B chromosomes into two groups of three plants each, a "low association" group with means of 0.03III + 4.43II (1.55 rings + 2.88 rods) + 5.10I and 6.03 chiasmata/cell, and a "high association" group with means of 0.01IV + 0.03III + 6.40II (3.55 rings + 2.85 rods) + 1.13I and 10.04 chiasmata/cell. The low number of plants studied prevents a safe estimate of the number of genes involved, but the significant difference between groups suggests the presence in the rye genome of two major genes, or two genotypes, for control of meiotic chromosome association. In two additional hybrids with 2n = 25, one of each above-mentioned group, the presence of two extra rye B chromosomes raised chiasma frequencies by ca 1.5, indicating a promoting effect on chromosome association. The level of Hordeum chromosome association in the "high association" group and the observation of up to 7 Hordeum ring bivalents in some cells agree with an autoploid origin of H. marinum ssp. gussoneanum (4x). Hordeum and rye chromosomes formed a few heterogenomic bi- and trivalents. Most rye A chromosomes formed univalents, but 2.7% were included in associations. Rye B chromosomes generally formed rod bivalents. The use of genome analysis in its traditional sense is discussed.
Linde-Laursen
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IB
Plant Biology and Biogeochemistry Department, Risø National Laboratory, Roskilde, Denmark.
von Bothmer
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R
D002875:Chromosomes; D003433:Crosses, Genetic; D017343:Genes, Plant; D001467:Hordeum / Q000235:genetics*; D008540:Meiosis / Q000235:genetics; D008677:Metaphase; D012434:Secale / Q000235:genetics*